Notes for Editors

“Global maps of anhydrous minerals at the surface of Mars from OMEGA/MEx,” by A. Ody et al., is published in the Journal of Geophysical Research 117, (2012).

“Global investigation of olivine on Mars: Insights into crust and mantle compositions,” by A. Ody et al., is published in the Journal of Geophysical Research, 118 (2013).

“Hydrous minerals on Mars as seen by the CRISM and OMEGA imaging spectrometers: Updated global view,” by J. Carter et al., is published in the Journal of Geophysical Research 118 (2013).

OMEGA observationsThe new maps are based primarily on data collected by the visible and infrared mineralogical mapping spectrometer, OMEGA (Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité). It determines mineral composition from the visible and infrared light reflected from the planet's surface in the wavelength range 0.5–5.2 microns. As light reflected from the surface must pass through the atmosphere before entering the instrument, OMEGA also measures aspects of atmospheric composition.

However, the atmosphere is so dense over the 9 km-deep Hellas Basin that detections from the crater floor cannot be made by OMEGA, resulting in the data gap seen on the maps. The vast distance between the surface to Mars Express also impairs measurements over the smaller Argyre basin just to the left of centre in the southern hemisphere. Seasonal carbon dioxide and water ice frosts occurring in the polar regions restricts observing periods and spatial coverage in these regions.

OMEGA maps the surface composition in 100 m squares. It samples the surface from ∼4.1 km/pixel down to ∼350 m/pixel, nadir-pointed. It has achieved 51% coverage at samplings < 500 m/pixel and near total coverage at samplings < 4.1 km/pixel.

The map showing hydrated minerals includes detections made by both ESA’s Mars Express and by NASA’s Mars Reconnaissance Orbiter.